1) Is there any evidence of factors which cause SP (stress, anxiety, depression, sleep deprivation, etc)?

Plenty. Traditional as well as recent (including my decade-long research) investigations have connected psychological and physical stress, anxiety, depression, and particularly sleep deprivation, to SP, even in the so-called normal population (those individuals who only report a couple of SP episodes in their entire lives). Generally speaking, any major life transitions (including dramatic shifts in sexual activity) that could generate stress are all factors to be considered in SP. The challenge now is to tie these triggers to neurochemical events and to SP. One possible connection is in the fact that antidepressant drugs such as imipramine have been proven useful in treating SP. Imipramine improves the availability of serotonin, a neurotransmitter that is also involved in both "agitated depression" and in REM sleep (and thus in SP).

2) Why does it almost always happen while in a supine position?

It doesn't always (not even almost always). It is true that a lot of subjects report SP while in a supine position. My answer to that is tied to a theme that I will use to approach your other questions. I refer to SP as "bounded lucidity" to describe both the paralysis and the self-awareness of the paralysis experience. In a supine position one still has "both ears to the world" so to speak, as opposed to laying on one side and depriving oneself from stimuli. A supine position is antithetical to the more natural fetal sleeping position, when humans first experience REM sleep. In a sense, a supine position is not a very natural sleeping position at all (even though lots of folks do it) when you think about it in these developmental terms. Functionally speaking, sleeping on one's back may preserve a state of vigilance and therefore lead to the greater probability of self-awareness during REM sleep. Several pre-dormittal behaviors that demand some degree of vigilance, like reading or watching TV, are done from this position. If one moves back and forth from being awake to REM states (which is very easy to do since they both reflect beta cortical activity), the separation between both states could become non-existent. Finally, a lot of my subjects do report SPs in a supine position when they take naps. Once again the dormittal context is not one of "I intend to sleep in a fetal, primal position," but rather one of "Ooops, imagine that, I fell asleep on my couch while waiting for..." Under these 'propitious' circumstances, once again, vigilance could be maintained into REM proper. Kleitman, the co-discoverer of REM sleep (1955), and others have shown that there exists a basic rest activity cycle (BRAC) throughout the 24-hour cycle. The same 90-minute cycle is maintained by the alternating contribution of non-REM and REM periods. In this sense, being awake and being asleep are: a) subordinate to a larger physiological arousal event, and b) on a continuum. Finally, breathing patterns may also be altered while in a supine position, as in the case of sleep apnea, giving rise to sub-optimal, intermittent rest.

3) Could you describe the neural activity during SP?

With the risk of oversimplifying, SP can be described as the self-awareness that one has slipped into REM sleep. So in order to understand SP, one has to understand REM sleep. Rapid Eye Movement sleep, REM, is a concerted co-activation (and deactivation) of several medullar and forebrain systems. This concerted activation (and deactivation) leads to multiple REM sleep phenomena: inhibition of certain motor neurons; inhibition of sensory input; rapid eye movements; activation of brainstem neurons that control the movement of facial muscles; and important to the hallucinatory experiences associated with SP, the activation of visual pathways. These events normally occur when neurons in the pons (a medullar structure) become active after a period of non-REM sleep (slow-wave, synchronized sleep). All these events are also associated with beta cortical activity; the sign of an alert brain. In fact, REM sleep used to be called "paradoxical sleep" because it resembles beta cortical activity in awake brains during a sequence that is preceded by almost "comatose" cortical non-activity. At least eight distinct medullar and forebrain structures are known to be involved in sleep and arousal in general, and (at least) three major neurotransmitters mediate operation of these systems (serotonin, acetylcholine, norepinephrine). To the preceding description one has to add the fact that SP sufferers are able to enter these states bypassing the non-REM stages of sleep.

4) What is the difference between dream images and hallucinations? Which are SP sufferers experiencing?

It depends on your perspective. By that I mean that if SP is self-awareness of a natural motor-inhibitory state, occurring during REM (so that we cannot act out our dreams), then one hallucinates of course. To put it simply: if I "wake up" with total self-awareness during the normal sleep paralysis of REM and experience a dream, it would seem as a hallucination to me. In this sense dream images (or other actual events occurring in the bedroom of the sleeper) are interpreted as 'real', as hallucinations. (Hence the alien abduction phenomena and its misinterpretation as 'real.') Thus, normally occurring dream images happen concurrently with enhanced self-awareness, leading to increased awareness and the intensification of ANY reality. However, distinguishing between images versus other emotions may be more relevant to the study of SP. For example, "feelings" of oppression, chest pressure (the "old hag", the incubus) have been reported in stage four of non-REM sleep, not in REM. But then again, immediately after stage four, REM sleep follows with the greater probability of introducing the visual imagery absent in a generalized "feeling of pressure" in the earlier stage. If these are sequential and rapid events, the overall report from the dreamer's perspective might include information about the "feeling" of pressure and the images that follow.

5) What is the difference between SP just before falling asleep and SP just upon waking up?

In a lot of cases, Sleep Onset Paralysis is an indicator of sleep deprivation or associated with narcolepsy (in narcoleptics). From MY theoretical perspective, phenomenologically speaking, it makes no real, functional difference. That is, subjects' intense imagery and anxiety is equal in both cases. My subjects report the sleep onset paralysis more than the latter. In terms of the imagery that might be associated with SP, sleep onset paralysis is such an abrupt transition from awake-cortical-activation to REM-cortical-activation (beta to beta in a nanosecond!), that the line between the real-external and the real-internal might not be distinguishable.

6) What is the difference between isolated SP and SP in narcoleptics?

Isolated Sleep Paralysis is reported by non-narcoleptics. Depending on what study you read, between 5 and 16% of the normal population report Isolated Sleep Paralysis without any other symptoms. Going back to my "bounded lucidity" theoretical frame of reference, self-awareness coincidental with REM cycles is common to both narcoleptics and non-. Nor all narcoleptics experience SP. The continuum of narcolepsy encompasses symptoms from being unusually tired during the day to extreme cataplexy and loss of body tone.

7) What are some of the latest developments in studies conducted on SP?

Ohayon et al (1999) did a comprehensive study looking at many variables associated with SP. Although tilted toward the clinical side of SP, it is a remarkable study. Takeuchi et al's (1992) provided evidence that SP can be induced by interrupting sleep. This opens the door for the hypothesis that multiple trigger events can contribute to arousal during sleep, and thus to a greater chance of SP. But the classic literature is still pertinent to present-day efforts. For example, the study by K. Firestone (1985) on the phenomenon of the "Old hag" in Newfoundland is a very fascinating story. Interesting and scientifically inspiring work is being done by research teams in Canada and the UK as well. Humbly, my own unorthodox ideas is that SP, being the phenomenon of an unstable electrochemical machine, the sleeping human brain, is entrainable by naturally occurring geomagnetic phenomena. I don't know the end of this story yet, but the initial chapters are tantalizing. Imagine a truly ecological explanation of dream events that includes the effects of geomagnetic field changes occurring across historical time or from moment to moment! If this happens, dream events, in addition to being introspective phenomena, can be used as a psycho-historical, or if you wish, a psycho-social indicator. Could moments of historical (or social) instability be (retrospectively) analyzed via archival dream reports and be found to be contiguous with abrupt geomagnetic changes? Have the arts, prophecy, or epic narratives been precipitated by such circumstances? This is indeed an exiting time for SP theory and research!

8) Do we know of any animals which have SP? (Dogs, of course, are well known to have narcolepsy)

I don't know of animals other than humans who experience SP. That would be a hard scientific case to make because to me, SP and self-awareness go hand in hand. One would have to show self-awareness (and a means of reporting this experience) in animals while showing evidence for SP. Of course, researchers might show EEG data of cats, going into REM sleep very fast and suggest that it is SP. How does one prove it though, without the language, without the subjective report? Without the story-telling, there are only squiggly lines. As you indicate, dogs do it and goats too, by the way (are narcoleptic)! Are they self-aware during the episode? Is there cognition going on during these lapses? Let's give them the benefit of the doubt and say...perhaps. Those are interesting empirical questions. But if Fido dreams of alien abductions, aliens must be real (a truly independent, trans-species confirmation).

9) What advice would you give to prevent SP? What about during an SP attack?

NONE! I have suffered from chronic ISP since my teens and now, in my late forties, having conquered the fear of the paralysis, I find that SP can be a gateway to lucid dreaming. However, if the person is new to the experience and the fright is too intense, there are several "techniques" that our subjects have shared with each other and with me that can control the episode. What all these techniques have in common is the manipulation of attention. One very effective technique is to concentrate on a point two inches below the navel while breathing calmly. If this trick can be learned, the SP episode slips into a regular dream or the person wakes up. Of course any attentional technique may prove to be equally useful.

10) If SP sufferers are only experiencing dream images and/or hallucinations, how come they all describe very similar things, such as figures, hearing footsteps, etc?

Most adult dreamers, male and female (Van de Castle, 1994), report dreams where "figures" or sinister entities are after them. Homo Sapiens is, by virtue of his/her social condition, Homo Paranoidensis too. To the extent that normal dream imagery without SP visits these themes, why wouldn't, then, SP (as any other REM) phenomena be about the same things we dream about? The constancy, the invariants are in the "normal" dream reports to begin with. And then there is the mundane explanation: in a state of beta cortical activity (lucidity) while registering information dually from inner and outer worlds, neighbors will walk across rooms and any of these real outside elements could mingle with dream experiences culminating in a "hybrid" reality (where real footsteps are heard).

11) Is there a connection between the "sensed presence" in SP and in normal waking life (eg. people sensing someone is looking at them or behind them)?

Do you mean a correlation between stranger-in-the-street paranoia and the FOP (feeling of presence) during SP? I don't know that this relationship has been established. Of course psychoanalysis has had a field day with SP experiences to the extent that any insecurity feeling, feelings of persecution and other subconscious processes were assumed to give rise (causally) to SP (they may or may not). There is an interesting note related to your question though. In a famous study by Dement (1976), subjects who were deprived of their sleep for four days became paranoid. Some of them believed that the experimenters were trying to harm them (well, I would too after four days without sleep). Interestingly, teenagers who are living under the effects of a developmentally inflicted sort of paranoia, the "imaginary audience", do not report more FOPs than adult sufferers (see below).

12) At what age does SP most occur and why?

Puberty seems to be the starting point for a lot of SP experiences, although children as young as 10 report SP phenomena. Given my own data, there is a critical window for an increase of SP reports. This critical window happens between ages 18 and 27. This seems to coincide with the transition between adolescence and young adulthood. This period of human development is coincidental with major life transitions, including peak sexuality, dramatic changes in sleep patterns, new professional or educational obligations, extraordinary physical output, etc. Any of these causes of stress can alone be a trigger for SP. Outside of this developmental window, the likelihood that a person will report SP episodes is a stable trait: a small percentage of individuals report SP episodes throughout their lives. Critical to a Melatonin Hypothesis* that I proposed, the elderly do not report SP as frequently. The pineal gland, which produces melatonin during the night, ossifies, calcifies with age.

13) Is there a genetic link to SP?

SP is definitely FAMILIAL. The fact that SP is familial allows for that probability. Dement observed and reported familial effects while studying narcolepsy in the seventies, and low and behold, today the same team has isolated the chromosome responsible for the syndrome (at least in dogs). But one has to be cautious about drawing causal connections between the occurrence of SP in families and a genetic link per se. It could be that family habits (nurture) and not a gene predispose some individuals more than others. Now that the Stanford team (headed by Dr. Mignot) has isolated the gene responsible for narcolepsy in an animal model, that gives us hope that the same can be done for SP. The gene was located on the 12th chromosome.

14) Why does SP and narcolepsy seem more prevalent in Japan? Are there certain countries that have higher number of cases than others and why?

I have argued that "special populations" may hold the key to understanding SP across the board (in all fairness, other researchers have argued that much). If there are genetic or cultural (or both) components to SP, these populations represent important case studies to isolate these variables. One also has to consider the possibility that some cultures pay more attention to the phenomenon and therefore may over-folklorize SP, making its incidence seem unusually high. On the other hand, and biologically speaking, examples of "bottle necks" in the gene pool exist for behaviors and physiological propensities. Island nations such as Japan, Indonesia, and Fiji that report SP as part of their folklore were also isolated from larger populations for extended periods in history. Their gene pools could over represent sleep disorders. Additionally, African (Nigeria) countries have reported a higher than normal (Ohaeri et al, 1992) occurrence of SP. Other examples of island or remote populations are to be found in the classical SP report by Firestone in Newfoundland (1985), reports by mental-health providers treating the Inuit in the artic regions of Canada, and finally, reports from folklore in Central America. Yes, there are many reported "bottle necks".

15) Do you think SP explains many cultural folklores, such as "old hag" and today, alien abductions?

Yes, I do. We should first (and secondly) explain the seemingly fantastic via common sense scientific explanations. SP hypotheses must be testable, falsifiable. If we use the term SP to include a combination of phenomena (sleep paralysis, hallucinations, etc.) then there is no question in my mind that the "old hag" experience is SP. With the same qualifications, there is no question in my mind that Hawaiian Night Marchers experiences are SP. There is no question in my mind that Kanashibari in Japan is SP. There is no question in my mind that Indonesian Tindihan is SP. There is no question in my mind that the sleeping dead of Fiji are accounts of SP. There is no question in my mind that reports from the shamans in the Canadian Artic or those from the Mayans in Guatemala are also accounts of SP. Are alien abductions accounts of SP? Yes, those too, with a twist: the traumatic memories of a newborn looking at the environment of an operating room, with fuzzy vision, being confronted by chopped bodies dressed in uniform garbs and masks.

16) In your opinion, is SP a disorder that needs to be looked at considering it is ultimately harmless?

Depending what you mean by "looked at", yes and no. Any psychological-medical phenomenon of interest should be looked at because "it's there". More importantly, any disturbance, if it leads to dysfunction (it prevents one from holding a steady job, conflicts with family life, produces intense, unbearable emotions, etc.) for more than six months, needs to be addressed. It is an issue of wellness. In that sense "it needs to be looked at". However, for most of the subjects that I get information from, SP is at best a temporary and harmless event even though it is very disturbing to them. For the fewer who have had SP throughout their lives, they also manage. Some have incorporated the more creative aspects of SP into their lives (lucid dreaming). I have lived a fairly normal and productive life with chronic SP without medical intervention.

17) In your experience, what is the most extreme SP patient you have come across?

The subject, a female, reported up to half a dozen SP's in a month and up to 20 in a year. She was (is) very sensitive to any alterations of routines in her life. She experiences the FOP's, and other hallucinations, but she knows they are part of her dream life; she knows they are not real. Of course, I am taking her reports at face value.

18) What questions remain a mystery in SP? What fascinates you about SP?

Since I abhor mysteries, I would rephrase your question and say that there are three basic questions that need to be answered (for me). They are merely "unknowns" at the moment. One, we need a psychobiological explication of the SP condition across a wide variety of experiences, cultural settings, and personal situations (there might be several neurological mechanisms). I am putting my money on the notion that Melatonin synthesis will explain some of the neuro-chemical events that give rise to SP. Two, it would be very handy to have a genetic screen for SP, just for the fun of it. But this is a pie-in-the- sky kind of wish because, luckily, 99.99% of SP sufferers are in no immediate danger. Three, there is also the connection between SP and creativity. Can the experiencing of SP on a regular basis be a predictor of creativity? Finally, the one aspect of these experiences that continues to fascinate me is that SP is a portal to an extreme form of personal entertainment. That is, SP can be a gateway to lucid dreaming and as such, it can add an entire new element of nightly experience. If you permit me this indulgence, and quoting myself: "...this state of bound lucidity and cortical beta coherence does more than agonize in paralysis. Self-awareness can adapt in the creative state of hypnagogic hallucinatory states and gives rise to multigenerational and cross-cultural dream stories. The 'ghosts', the 'incubi' and the 'hags' in turn invent culture." If culture is partly invented by dreams, by SP reports, then future culture can be made better (?) by controlling them. Stephen LaBerge, the world authority on lucid dreaming, has expressed sentiments along the same lines.